Centrifugally-cast circular ingot



June 18, 1935.

Filed Dec.

INVENTOR Patented I June 18,. 1935 UNITED STATES PATENT OFFICE r2,005,175 CENTRIFUGALLY-OAST CIRCULAR moor James L. Adams, Jr.,Youngstown, Ohio Application December as, 1932, Serial No. 649,181

3 Claims.

The presentinvention relates broadly to the art of ingot making, butmore particularly to the high-speed centrifugal casting of relativelywider and thinner than usual circular ring ingots, in

. which the successive stages of solidification have been appropriatelycontrolled so as to give great solidity'and density to the resultantmass, with substantially complete elimination of the cus-. tomary pipes,shrinkage cracks, blow-holes, gaspockets, blisters, non-uniformity ofcarbon-distribution, variations of chemical structure and crystalformations, and slag and other non-metallic inclusions common to theusual ingot of commerce, in which considerable segregation, or

5 separation of the several constituents of the molten mixture, normallyoccurs during the initial cooling and solidification.

My invention also covers an ingot in which certain surfaces, or at leastone surface, has been preferably hot-trimmed after solidification, tobetter prepare the metal for subsequent belt-mill rolling, and removeun-wanted surface inclusions.

Some of the primary objects of the present invention, therefore, consistinthe provision of a metal ingot which is (1) uniformly dense and solidthroughout, within very narrow plus and minus limits, (2) ofsubstantially uniform chemical composition, and if of steel, then ofvery uniform carbon-content throughout, (3) that is substantiallywithout interior piping and fissures, or

shrinkage cracks, (4) that has been substantially freed of slag,non-metallics, and low-density metallic inclusions, (5) is very low ingas-inclusions, (6) that has been trimmedto remove at least interiorsurface irregularities and non-desired elements, ('7) which is of theextra wide and the thin walled type, and (8) has substantially all ofits coarser, radial-cleavage-plane type of crystal structure locatedjust below the outside diametral surface, where it is readily brokendown intofrom one of the broad surface faces toward the other, acrossits thinnest sectional dimension, under such heat control as toeliminate all interior piping, and inner diameter sub-surfacecrystalslip planes, and avoid the imprisonment of non-desired slag and gases.

A further object of value was to supply an ingot of such shape that therolling will elongate the entire mass together, and not have to "pulloutmetal that is well away from the roll surfaces, as in the usualsquare orrectangular ingot.

That is, the latter type of ingot has, to begin with, a heavysub-surface layer all around, of coarse, weak metal crystals withoutwardly. directed inter-crystal cleavage envelopes, which will not.stand very much ingot elongation without separation tending to occurbetween successive crystals, and thus opening up the surface and nearsurface layers to the entry of air and oxygen. The first pass throughthe rolls breaks down these crystals into a finer and tougher grainedstructure, capable of standing far more stretching out abuse thereafter,but in a rectangular straight type ingot the first pass, unfortunately,does not contact with but two faces of the ingot. The metal on the othertwo main faces must however stretch very considerably-during this firstpass, although the crystals there have not yet been worked between therolls at all, and are, in consequence, still very brittle and weaklongitudinally of the ingot, so that a certain amountof opening up ofthe crystal surface and near-surface elements occurs, very detrimentalto the final sur-' face layers here after the rolling. In my ingot,however, the percentage of the total ingot surface that is not directlyreached by the first pass through the rolls is almost negligible, andthe general thickness of the ingot is so vastly much less than in thecustomary straight rectangular ingot, that substantially all of ther0ll-to roll metal at any given instant is being extended about equally,and not part being lengthened while the larger bulk holds-back in thepiece, and has to r be pulled-out and its crystals separated by theformer, by sheer strength and awkwardness.

The net result is that my ingot gives a much better knit final surfacestructure, and at the same time a far more rapid reduction to therequired size in the mill.

greatly cut plate and sheet manufacturing costs, by providing atypeofingot eminently suited for use in connection with a high-speed andhighcapacity, continuous belt-mill, such, for example, as that shown anddescribed in my co-pending application, Serial #674,661, filed June 7th,1933.

One leading object is to substantially eliminate the now usual 15% to25% end-crop loss, necessitated by the customary interior piping andsolidification fissures.

Another important object is to provide an ingot which has not only beencentrifugally cast at high-speed to assist in densifying and-purifyingthe metal, but which has been jarred" or shaken also, during itssolidification period, if desired. so

Another vital object of my invention is to Y as to better get rid of gasinclusions, through the more or less viscous metal.

Another object is to get'an ingot in which the non-desired inclusionshave been delivered substantially in toto, to the smooth interiorcylindrical surface, where they are readily hotor coldtrimmed away, tothus leave a clean metal product. I

Another object is to greatly cutthe usual solidification time, and thesoaking pit heating period, by supplying a relatively thin walled ingot,of broad expanse. I

An outstanding object is to provide an ingot of such form as to requirea minimum number of passes through the mill to roll to requiredthicknesses.

A further object is to provide an ingot of such shape that it can bequickly and conveniently heated, or evened up in temperature, asrequired, either by gas or by oil flames, in a reducing'atmosphere, orinert gas envelope, if desired, or

electrically, by peripherally or otherwise circulating currents,preferably. produced directly in the metal by electro-magneticinduction, which can be made to automatically give the greaterconcentrations of current in the lower temperature belts around thering, and therefoiffe'the greater heating-up here, to provide (quickevening-up of temperatures therein.'-

A still further object met by a ringingot is that it may be rotated,v'ery readily around-its own axis during the heat-ing, if so desired,and thusfgive greatiuniformi tyi to the resultant temperature, even ifsome of the burners may be d'ffsizeh' Another object of my invention istoprovide an ingot so thin "ii section as to greatly fore-shorten thesolidificationtime', and thus the time :allotted both for segregation ofthe constituents'of the metal mixtuzfe, and for the growth in size ofthe metal crystals, thus leading at once toija more general uniformityof the chemical strueture, as wellas to a more refined graindevelopment, preparatory to rolling.

An added object is to provide an ingot so poured centrifugally, as tosubstantially eliminate the usual surface sliver, and tear, or dropletformations, and laminations, whichnow often carry over into the finalrolled surfaces, and cause numerous inspection rejections, withconsequent costly scrapping, as a result of splashing in the far cornersof the usual mould, during the pourmg. t

A supplementary object is to provide an ingot of such form that it maybe very conveniently hot-trimmed on at least one major surface, bywater-cooled rotary blade tools, which are the only known type capableof standing up for long periods of regular use, under the very highsurface temperatures encountered on a heated ingot, either just beforeit enters, or as it leaves the soaking pit, preparatory to rolling. Yetanother object is to provide a form of ingot which can be rolled intoultra lbngplates, or non-cut bands, as required, and of greater thanusual total weight per piece. the utmost advantage in electric pipewelding, to cut down the total end-scrap losses.

Other worthwhile objects will be obvious to anyone versed in the art towhich my invention appertains.

With all these and other objects in view, I have provided an ingot whichwill substantially fill such requirements, it being noted that myapparatus is capable of keeping the interior broad surface of the ingotliquid as long as may be de- Such very long plates are of' sired toassure that the solidification will be progressively from the outerperipheral face inward through the casting, and under such centrifugaland jarring conditions as to assure maximum compacting, but withoutextending such heating enough to permit the growth of large crystals,and extended segregation of the more easily separated components'of themetal.

'It will be further noted that I preferably hot trim at least one majorsurface of my ingot, so that the latter is supplied with surface minorinclusions eliminated substantially from this face, and with variationsin thickness of ring reduced to a form entirely amenable to laterrolling, without introducing side camber in the finished belt. Thus ifthe ring be somewhat thicker, at one point around the periphery thereof,this willintroduce no especial trouble in the rolling, provided suchextra thickness is not to severe, and provided further that it ismaintained constant for the full length of the ingot, and does not alterthe uniform heating.

Or if the mould be made somewhat conical in its interior, for easierwithdrawal of the ingots after solidification, such conicality will notnecessarily interfere with the production, nevertheless, of astraightbelt, provided the lesser end of the cone be madeproportionately thicker radially, so as to give anequal bulk of metal,and weight, per inch of axial length of ingot, preparatory to therolling.

It is not obligatory that my ingot be hottrimmed to meet the abovementioned conditions, as it might be conceivably so cast as not to needit, but I prefer trimming, and in my copending application, ,Serial#680,570, filed July 15th, 1933, I have illustrated and describedapparatus, and a method of producing the ingot of my present invention,while a further co-pending application, Serial #652,142, filed January17th, 1933, shows an ingot-buggy suitable for the quick and expeditioustransport of my ingot from soaking pit, and its delivery direct into mybelt-mill previously referred to, while under slow, continued rotationso as to not receive a chill in localized spots therearound.

While my improved ingot is particularly adapted for use in the belt-millof my invention, be-

fore referred to, it might conceivably be applied to other uses, wherecompacted, clean, pure metal, substantially 'free from slag inclusions,is required.

In the drawing, Figure 1 is a perspective elevation of my improvedingot, showing the approximate desired proportions thereof.

Figure 2, in similar perspective, shows a modified form, also amenableto easy rolling, it being noted that there may be a plurality of eitheror both of the types of general surface alteration shown, if desired foreasier ingot moulding purposes, without serious eifect on the finalshape 7 of the crystal structure over these latter or nontudinallyinto=an ultra-long narrow strip, or a square. Y

In all these figures, similar parts are designated by the samereference-numbers, successive letter subscripts being added todistinguish between the successive figures.

" Referring now more particularly to Figure 1, my ingot is shown at I,.while 2 and 3 indicate interior and exterior general surfaces thereof,respectively.

-In Figure 2, similar elements are indicated by 2a and 3a respectively,while at 4 and 5 are shown full length radial projections anddepressions, re-

spectively, the normal extent thereof being exaggerated considerably forthe sake of cleamess. In Figure 3, a coned ingot is shown, in which 6-6and 1-1 indicate the major and minor diameters, respectively, while 8and 9 refer to the respective wall thicknesses at these same ends, itbeing noted 9 is made substantially as much thicker than 8, as the majordiameter is to the minor, so that inch-by-inch of axial length of ingot,the same total weight will be presented. But these proportions may bealtered slightly to correspond with actual behavior of the ingot uponfirst rolling tests, to give a straight, non-cambered belt.

In Figure 4, at the left, progressive surfaces of inner solidificationare presented at 3c, l0 thru l5, and finally 20, while at the right Ihave shown roughly the general form of the resultant crystal lization ofmy ingot, in which at It is illustrated the substantially radiallyplaced, coarse, and initially weak outwardly directed, but sub-surfacedendritic structure, and at H the much smaller grained and tougher, freecrystal inner structure, while it shows the thin surface layer ofnon-metallic inclusions carried to the extreme interior position by thestrong centrifugal effect and the active shaking introduced during thesolidification period. Later on these latter are usually removed,as'indicated at 2'0 here. I make sure that the freezing of the ingotoccurs progressively as shown, by addinginterior .dis'tributed heat,-asand if required during the solidification interval.

These sub-surface dendritic, or tree-trunk like crystals show radiallypositioned and relatively very weak envelopes, or cleavage shells,which,.

however, if not opened up to oxidation by pulling apart, very largelydisappear during the first and second passes through the mill, becomingmore finely grained and tougher under the actual working. It will beespecially noted that the total amount of free edge surface, at the twoaxial ends of my ingot, and which is not directly contacted by the rollseven during'the very first pass there- .through, is very small indeed,so that practically all of the near-surface .dendritlc structure of my Iingot is broken down and toughened immediately, while very little of itmust be stretched out by the elongating ingot, without direct rollingthereover, or so as to pull apart and open-up the cleavage shells, orplanes, and thereby give a porous, 'oxidized, and materially weakenednearsurface layer.

It'will, however, be equally noted that in the ordinary straightrectangular ingot of commerce, certainly not over about 60% to 65% ofthe total outer dendritic surface ,layer can possibly be reached duringthe first pass through the rolls. But the ingot .as a whole, andtherefore its remaining two major faces along therewith, must stretch orelongate nevertheless, thus breaking open for the free entry ofair andoxygen, much worked faces, which'it is then hoped will weld togetherproperly again during the next pass, after a 90 degree turn. of theingot.

' But such welding may, or may not, actually ocour to the full valuedesired.

In my ingot, however, substantially all of this detrimental effect isobviated, it being noted, from my co-pendlng application above referredto, that I even provide means whereby the narrow end faces of my ringingot may be rolled down likewise during the very first pass throughthe'mill, if so desired.

In Figure 5, I have shown axially-directed -ofl"-. set and elements,exaggerated for the sake of cleamess, and which would normally give anunstraight and camberless belts were required, but which, in the helicalspiral or screw form shown at l9 and 20, might conceivably roll out intoa desirable type of belt, provided the latter were to be spirallyslitted into an ultra long final strip,

in which case the offsets would permit a' material shaped final form, sothat the forward end of one can he slipped just within the trailingaxial end of the preceding, and so on indefinitely. v

In such cases, the conical ingot of Figure 3, or the straight sidedproduct of Figure l, may be supplied to the mill with one axial-end verydesirable form of ring-ingot,. where precisely slightly thickened upradially, beyond the value originally intended in the respectivefigures.

This will then produce a slightly coned belt, or one which, if later cutacross, will develop an edgecurved or cambered plate; if such weredesired.

From my co-pending ring-ingot producing apparatus application, abovecited, it will be noted. that I centrifugally rotate such ingot duringpreferably the entire pouring and solidification period, and that as,and if desired,'I may also jar the said ingot during all, or selectedportions of such period, as determined.

Certain very definite advantages accrue to an ingot produced in thismanner. 'I'hejarring very radically accentuates the elimination ofgases, particularly, over what is possible under a straight centrifugalprocess.

Other very decided advantages accrue from the fact that I hot-trim theinterior surface thereof,

at least, and thus deliver an ingot substantially free from slag, andnon-metallic inclusions.

Further definite advantages accrue in my ingot from the control of thesolidification so as to restrict it to a single inwardly progressivelycylinder of solidification at any one instant, whereby all interiorpiping and fissures are avoided.

Other important advantages accrue thereto because of its high percentageof actual rolling surface, compared to the idle areas within the ingot,

whereby high percentages of reduction per pass become possible; thusgreatly expediting the rolling, enabling the latter to be completedduring higher than normal temperatures and therefore with lessdestructive work on the metal structure, so that a much greater thanusual total reduction and elongation can be readily reached.

Other advantages arise from my ingot requiring a ,far less time thanusual in the temperature equalizing furnace or the soaking pit, becauseof its thin wall, and shape which is very favorable forItemperatureequalization in a short period.

Very decided advantages accrue from the fact that my ingot has beenproduced under conditions which give it a far' greater uniformity ofcarbon-content, in case the metal used is steel, than has heretoforebeen customary in the usual straight ingot of commerce, wherein thecarbon may be very decidedly different at the top than at or near thebottom, and also with local spots of divergent carbon percentages.

Other advantages accrue from my ingot being of a form which can beslowly rotated during transport hot to and from the soaking pits, thuseliminating the customary cooler spots dueto the usual prolongedcontacts with cold metal parts, before reaching the rolling-mill rolls.

Yet other advantages accrue from my ingot having been so cast as toavoid substantially all splashing of the molten metal from thefarthermost points of the mould, as is customary for the straight-ingotmould, with consequent formation of surface defects of numerous types inthe resultant ingot of commerce.

An added advantage accrues from the combination of all the abovementioned advantages in one and the same product.

Still further advantages will be evident to anyone versed in the art ofingot making, and although I have shown several preferredembodiments ofmy invention, it will be understood that moderate changes in the formand construction thereof, may be made without departing either from thespirit of my invention, or the scope of my broader claims.

I claim:

1. A cast ring-ingot with substantially helically directed end-faces, onits axially disposed ends. said end-faces forming offset elements withrespect to main body of ring-ingot, but included between inner and outerradii of latter.

2. An exteriorly straight-line coned ring-ingot with constant weight perrunning inch along its generating axis, and with a helical offsetlocated on'each end thereof, as taken in axial direction.

3. A cast ring-ingot with straight-line coned outside generated surface,with constant weight of metal per axlalrunning inch therealong, andmadeof a steel'characterized by all the qualities imparted. by concomitantcentrifugal casting, and jarring, during the pre-solidification periodthereof.

JAMES L. ADAMS. 'JR.

